As the siliceous film has a highly heat resistance, a good abrasion resistance, an excellent corrosion resistance, etc., it has been widely used for a long time as an insulation film provided between a semiconductor substrate and a wiring metal layer, between wiring metal layers or on various elements on the semiconductor substrate, an element separating film between various elements provided on the semiconductor substrate, a passivation film, a protective film, a planarization film, a stress adjusting film, a sacrifice film, and the like in the semiconductor device; and an insulation film provide between a glass substrate and an ITO film, between a transparent electrode film and an alignment film, and the like, a protection film provided on a pixel electrode, or a color filter in a liquid crystal display device. The siliceous coating film used in these fields was generally formed on a substrate by a vapor phase growth method such as a CVD method and a spattering method or an application method using a coating liquid for forming a siliceous film. Of these methods, the application method has been widely used in recent years because the vapor phase growth method has problems such that it takes time and needs a large facility and a flat surface cannot be formed on an uneven surface when a coating film is formed on the uneven surface.
By the way, in the field of the electronic devices such as a semiconductor device, higher density and higher integration thereof have been advanced in recent years. To meet these higher density and higher integration, a trench isolation structure, which is prepared by forming a fine trench on a surface of the semiconductor substrate and filling an insulator in the trench to electrically isolate between elements formed on the opposite sides of the trench, is adopted
When the aforementioned element separating films having a trench isolation structure are formed by a CVD method, a high density plasma CVD method, etc., a void may be formed in a fine groove. In addition, a method in which an alkoxysilane solution prepared by using a sol-gel method is applied on a substrate and then the coating film formed is converted into silicon dioxide by a heat treatment is considered (for example, see Patent document 1 below). However, in this method, cracks could occur by occurrence of volumetric shrinkage when alkoxysiloxane was converted into silicon dioxide.
As a method for suppressing occurrence of cracks described above, it was proposed to use a polysilazane as a precursor of silica (silicon dioxide; SiO2) (for example, see Patent documents 1 and 2 below) and this method is widely used now. As a composition containing a polysilazane has good burying properties in a trench isolation structure, there is an advantage that voids do not easily generate. For example, when a polysilazane such as perhydropolysilazane are buried in a trench and processed in an oxidation atmosphere, it is known that a siliceous film with high purity and high density is formed. However, a baking step at a high temperature which is generally called annealing is added in forming a siliceous film. At this time, the annealing is performed in a nitrogen or oxygen atmosphere but there exist problems that a film with sufficiently high density is not formed and the etching rare of the film formed becomes fast. It is necessary to control the thickness of the buried silica film by etching but at this time, when the etching rate is fast, an error to the target film thickness becomes easily large. It is, therefore, desirable that the silica film after annealing has a late etching rate. It is possible to make the etching rate lower by the high temperature annealing in a water vapor atmosphere but there occurs a problem that materials other than the siliceous film, no oxidation of which is desired, are oxidized too. In addition, it has been known that the surface of the silicon wafer is oxidized under a water vapor atmosphere or oxygen atmosphere of 400° C. or more and the increase of the film thickness by oxidation is produced. For example, in the production of a flash memory etc., it is necessary to keep the temperature of a water vapor or oxidation atmosphere 400° C. or less for avoiding irregularity of the height on the top surface of the silicon substrate due to the increase of the film thickness. Therefore, the water vapor processing and oxidation processing at a high temperature have not been acceptable in the technical field of manufacturing a semiconductor. Furthermore, it is necessary that STM and PDM formed from perhydropolysilazane is a high purity SiO2 film. The reason is that if impurities such as metal, carbon etc. left in the film, the device properties are badly affected.
The formation of a siliceous film in a trench by the application method are not limited to the method using a polysilazane described above. It has been performed by a suitable method, for example, such as a method using a silica solution prepared by a sol-gel method. However, in this method, it is also required to make the etching rate slow, as the etching rate becomes fast after annealing in an inert gas atmosphere as with a polysilazane. The specific explanation about the element isolation film (STI) has been performed hitherto, but the requirement of improving the etching rate of the siliceous film is same in the formation of an insulation film such as an interlayer insulation film (PMD), a passivation film, a protective film, and a planarization film.